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Q: Fachverband Quantenoptik und Photonik
Q 55: Poster Laseranwendungen
Q 55.4: Poster
Donnerstag, 13. März 2008, 16:30–19:00, Poster C2
Detection of NO isotopologues with a Quantum Cascade Laser based Faraday Modulation Spectroscopy — •X Sabana, Thomas Fritsch, Peter Hering, and Manfred Mürtz — Institut für Lasermedizin, 40225 Düsseldorf
The detection of 14NO and 15NO enables to analyse endogenous as well as exogenous sources. Faraday Modulation Spectroscopy (FAMOS) is a method used to detect NO with high sensitivity and without any cross-interferences.
FAMOS uses a Quantum Cascade Laser (QCL) because of its narrow linewidth and high optical output. It is also able to be frequency modulated up to about hundred MHz. This allows to improve the sensitivity of the detection using the double modulation technique. The double modulation technique is a combination of the laser frequency modulation and magnetic field frequency modulation with detection at the sum frequency.
The QCL used in our laboratory operates between 1839.9 cm−1 and 1851.9 cm−1 at a temperature between −30oC and 30oC and a maximum power of 27.4 mW. The laser power at the wavelength of the used NO transition is in the 1 mW range.
The NO transitions are in the frequency range of the QCL at 1842.94 cm−1 (14NO) and 1841.76 cm−1 (15NO) and the detection limits are 70 ppb (parts per billion) for 15NO and 380 ppb for 14NO with an integration time of 300 ms.
Because of its high selectivity, the FAMOS technique is an excellent method for measuring NO production from aqueous solutions.